Betta Fry don't eat algae-they do, however, feed off the micro-organism that feed off the algae (marimo ball) for the first 5-10 days of free swim stage....it can take several weeks for enough micro-organism to form/colonize on the algae balls (marimo ball)...this is based on few fry and lots of algae in a mature tank with common snails.

its because of the poop. i dont like siphoning becuase me not buying siphone and i made my own and water sometime gets in my mouth and i don't wanna get snail poo in my mouth and use alot of moutwash and toothpaste to get it out.